Fix Typos in Documentation

[Marcofann]

This pull request addresses several minor typographical errors in documentation and comments across five files in the project. These changes improve clarity and maintain consistency without altering the functionality of the code.

Summary of Changes

1. host_integration.rs: Corrected article usage in comments.
2. server_integration.rs: Fixed article consistency in a comment.
3. lib.rs: Adjusted grammar for HTTP server documentation.
4. server.rs: Resolved typo in gRPC-related comment.
5. rollups_inputs.rs: Improved article usage in enum description.

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Guidelines Followed

• The PR focuses solely on fixing typos and does not include any functional changes.
• Each file addresses a specific typo, and changes are isolated for review simplicity.

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Checklist

• Detailed description provided.
• Changes follow the project's Contributing Guidelines.
• PR does not introduce functional or behavioral changes.
• Tests are not applicable for comment/documentation changes.
• Verified changes do not affect the output of existing tests using make test.